Genetic Differentiation of Populations of the Threatened Saproxylic Beetle
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Biological Journal of the Linnean Society, 2015, , –. With 4 figures. Genetic differentiation of populations of the threatened saproxylic beetle Rosalia longicorn, Rosalia alpina (Coleoptera: Cerambycidae) in Central and South-east Europe LUKAS DRAG1,2*, DAVID HAUCK2,SANDOR BERCES 3, JAKUB MICHALCEWICZ4, 5 6 1,2 LUCIJA SERIC JELASKA , SANDRA AURENHAMMER and LUKAS CIZEK 1Faculty of Science, University of South Bohemia, Branisovska 31, 37005, Ceske Budejovice, Czech Republic 2Biology Centre CAS, v. v. i., Institute of Entomology, Branisovska 31, 37005, Ceske Budejovice, Czech Republic 3Duna-Ipoly National Park Directorate, Kolto utca 21, 1121, Budapest, Hungary 4Institute of Forest Ecosystem Protection, Faculty of Forestry, University of Agriculture, Al. 29 Listopada 46, 31-425, Krakow, Poland 5Faculty of Science, University of Zagreb, Rooseveltov trg 6, 10000, Zagreb, Croatia 6Institute for Animal Ecology and Landscape Planning, Bergmanngasse 22, 8010, Graz, Austria Received 21 April 2015; revised 16 June 2015; accepted for publication 16 June 2015 Knowledge of patterns of genetic diversity in populations of threatened species is vital for their effective conservation. Rosalia longicorn (Rosalia alpina) is an endangered and strictly protected beetle. Despite a marked decline in part of its range, the beetle has recently expanded to the lowlands of Central Europe. To facilitate a better understanding of the species’ biology, recent expansion and more effective conservation measures, we investigated patterns of genetic structure among 32 populations across Central and South-east Europe. Eight microsatellite loci and a partial mitochondrial gene (cytochrome c oxidase subunit I) were used as markers. Both markers showed a significant decline in genetic diversity with latitude, suggesting a glacial refugium in north- western Greece. The cluster analysis of the nuclear marker indicated the existence of two genetically distinct lineages meeting near the border between the Western and Eastern Carpathians. By contrast, one widespread mtDNA haplotype was dominant in most populations, leading to the assumption that a rapid expansion of a single lineage occurred across the study area. The genetic differentiation among populations from the north- western part of the study area was, however, surprisingly low. They lacked any substructure and isolation-by- distance on a scale of up to 600 km. This result suggests a strong dispersal capacity of the species, as well as a lack of migration barriers throughout the study area. That the lowland populations are closely related to those from the nearby mountains indicates repeated colonization of the lowlands. Our results further suggest that R. alpina mostly lives in large, open populations. Large-scale conservation measures need to be applied to allow for its continued existence. © 2015 The Linnean Society of London, Biological Journal of the Linnean Society, 2015, 00, 000–000. ADDITIONAL KEYWORDS: beech – conservation – Natura 2000 – phylogeography – post-glacial recolo- nization – xylophagous insect. INTRODUCTION development of wide-scale conservation strategies and the use of management actions according to the An understanding of the patterns of genetic diversity current needs (Avise et al., 1987; Moritz, 1994). Pop- in populations of threatened species enables the ulation genetic structure is determined by genetic isolation, which is governed by the forces of genetic *Corresponding author. E-mail: [email protected] drift, natural selection, and gene flow (Slatkin, © 2015 The Linnean Society of London, Biological Journal of the Linnean Society, 2015, , – 1 2 L. DRAG ET AL. 1987). Furthermore, restrictions in the landscape known to occur in Western (Picard, 1929) and South- permeability can reduce gene flow between habitat eastern (Serafim & Maincan, 2008) Europe. Recently, patches and decrease the effective population size. they have also been repeatedly reported in Central Such populations are then more prone to the effects Europe, mostly from the floodplains of the Danube of genetic drift that decrease genetic diversity and and its tributaries (Jendek & Jendek, 2006; Cizek inhibit adaptability to a changing environment et al., 2009; Hovorka, 2011). As a result of a lack of (Frankham, Ballou & Briscoe, 2002). Simple conser- earlier records, it has been proposed that the beetle vation of species that neglects to consider its popula- spread to the lowlands of Central Europe only tion structure may thus fail to address isolated and recently (Cizek et al., 2009). Such a sudden expan- genetically eroded populations or, by contrast, reveal sion into the previously unexploited habitat accompa- the reservoirs of genetic diversity such as glacial nied by a switch in the host plant may indicate the refugia. Consequently, a broad range of molecular existence of distinct ecotypes of the species, associ- techniques have been used to understand the nature ated with upland and lowland forests or beech and of population structure, and they become an impor- other hosts. tant tool in many studies of threatened and protected Two scenarios for the colonization of Central species (Sunnucks, 2000; Morin, Luikart & Wayne, European lowlands were proposed, including down- 2004; Behura, 2006). slope colonization by nearby upland populations Saproxylic insects are a diverse group with high and colonization by a lowland population from else- ecological and economical importance (Grove, 2002). where (Cizek et al., 2009). A shift of upland popula- Genetic structure has occasionally been studied in tions to lowlands would either require a change in the important pest species (Horn et al., 2006, 2009; the species’ host and/or habitat preference or in the Salle et al., 2007; Carter, Smith & Harrison, 2010). quality of the newly-colonized habitat. Colonization The saproxylic guild, however, also contains a num- by a lowland population originating outside the ber of threatened species, and some of them serve as region would suggest the existence of a lowland lin- models for ecology, conservation biology, and/or as eage, adapted to different habitats and hosts. The umbrella species (Ranius, 2002; Buse, Schroder & host-associated population structure, in which popu- Assmann, 2007). Despite that, very little is known lations exploiting different resources are genetically about their population genetics, and this may com- distinct (Stireman, Nason & Heard, 2005; Ferrari promise conservation efforts; but see also Cox et al. et al., 2012), is well documented in phytophagous (2013); Oleksa et al. (2013); Solano et al. (2013); insects and demonstrates how the environment can Drag & Cizek (2014); Oleksa et al. (2015). impact gene flow, even in the absence of physical The Rosalia longicorn (Rosalia alpina; Linnaeus, barriers (Feder et al., 1994; Via, Bouck & Skillman, 1758) is an endangered and strictly protected saprox- 2000). ylic beetle. It is listed as a priority species under the In the present study, we analyzed parts of nuclear European Union (EU) Habitats Directive, which (microsatellites) and mitochondrial (cytochrome c oxi- makes it an icon of invertebrate conservation in Eur- dase subunit I; COI) DNA of > 30 populations of ope. Its distribution range covers most of Europe; R. alpina from Central and South-east Europe aim- from the Pyrenees, the Alps, and the Carpathians, to ing to identify the patterns of their genetic diversity Crimea, the Caucasus, and the Urals (Sama, 2002). and phylogeographical structure. A broad range of In the south, the beetle reaches Corsica, Sicily, the statistical methods were applied to test hypothe- Greece, and the Turkish province of Hatay. In the ses about presumed refugia and species history. By north, the species has experienced substantial comparing the genetic structure of populations from retreat because it has disappeared from Scandinavia, lowlands and nearby mountains, we attempted to most of Germany, Poland, and Czech Republic reveal the relationship between populations originat- (Slama, 1998; Lindhe, Jeppsson & Ehnstrom,€ 2011; ing from different habitats. Information on patterns Michalcewicz & Ciach, 2015). Despite a notable of genetic diversity in R. alpina populations may decline, the distribution of the species is rather con- increase our knowledge of the species’ biology and tinuous in two large mountain systems: in the Alps facilitate more effective conservation. and the Carpathians, as well as on the Balkan Peninsula (Slama, 1998; Gepp, 2002; Duelli & Wer- melinger, 2005). MATERIAL AND METHODS Although generally considered a montane species associated with European beech Fagus sylvatica L. SAMPLE COLLECTION AND DNA EXTRACTION (Heyrovsky, 1955; Slama, 1998), R. alpina also The material analyzed included beetles from 33 local- inhabits lowlands and utilizes a wide range of broad- ities in Central and South-east Europe, thus covering leaved trees. The lowland populations were for long a significant part of the species’ distribution in © 2015 The Linnean Society of London, Biological Journal of the Linnean Society, 2015, , – POPULATION GENETIC STRUCTURE OF ROSALIA ALPINA 3 A B Figure 1. A, localization and the genetic structure of 32 populations (full names are listed in Table 1) of the Rosalia longicorn (Rosalia alpina) based on eight microsatellite loci. Each pie chart represents a proportion of membership of individuals from a given population in each of the two clusters indicated by the Bayesian clustering analysis (STRUC- TURE). Grey surface represents the area above 800 m